Can anyone recommend a visual multitrack software?

I want to combine visual shots and audio into one video and play them simultaneously (multitrack). Does anyone know of any good software to accomplish this that is compatible with OS X? Unfortunately, iMovie doesn't allow more than one "picture in picture". All help (including third party paid softwares) is greatly appreciated! Thanks!

Final Cut X, Adobe Premiere ... surely you did a search and already know of these?

I'm not sure what you mean by "visual shots," but it may be that you could do this quite stylishly in either Keynote or iPhoto/Photos if you mean pictures.